B3 Organization and the digestive system

Question 1

Simple sugars

Answer 1

Small carbohydrates consisting of only one or two sugar molecules e.g. glucose and sucrose

Question 2

Complex carbohydrates

Answer 2

Long chains of simple sugars e.g. starch and cellulose

Question 3

Tissue

Answer 3

A group of cells with similar structure and function working together

Question 4

Organ

Answer 4

A collection of tissues working together to perform a specific function

Question 5

Organ system

Answer 5

A group of organs that all work together to perform specific functions

Question 6

Food tests - carbohydrates

Answer 6

• Iodine test for starch, yellow-red iodine solution turns blue-black if starch is present
• Benedict’s test for sugars, blue Benedict’s solution turns brick red on heating if a sugar such as glucose is present

Question 7

Food tests - protein

Answer 7

Biuret test - blue Biuret reagent turns purple if protein is present

Question 8

Food tests - lipids

Answer 8

Ethanol test - ethanol added to a solution gives a cloudy white layer if a lipid is present.

Question 9

Lock and key enzyme theory

Answer 9

• The substrate of the reaction to be catalysed fits into the active site of the enzyme
• The substrate is complementary in shape to the active site
• Once it is in place, the enzyme and the substrate bind together
• The reaction then takes place rapidly and the products are released from the surface of the enzyme

Question 10

Metabolism

Answer 10

The sum of all the chemical reactions in a cell or the body

Question 11

Effect of pH on enzyme action

Answer 11

• The shape of the active site of an enzyme comes from forces between the different parts of the protein molecule
• These forces hold the folded chains in place
• A change in pH affects these forces, and the shape of the molecule changes
• As a result, the specific shape of the active site is lost, the substrate is no longer complementary in shape to the active site, the enzyme no longer acts as a catalyst

Question 12

Effect of temperature on enzyme action

Answer 12

• The rate of enzyme-controlled reactions increases as the temperature increases as molecules have more kinetic energy, only up until the optimum temperature
• The optimum temperature for enzyme action is approximately 37 degrees
• After this, the protein structure of the enzyme is affected by the high temperature and the active site changes shape
• The substrate will no longer fit in the active site, the enzyme is denatured and can no longer work as a catalyst
• The rate of the reaction drops dramatically

Question 13

What are carbohydrates made up of?

Answer 13

Simple sugars

Question 14

Function of small intestine

Answer 14

Digest food and absorb nutrients from digested food

Question 15

Function of large intestine

Answer 15

Absorb water from digested food

Question 16

Function of the gall bladder

Answer 16

Store bile before release into small intestine

Question 17

Function of liver in the digestive system

Answer 17

Produces bile for lipid digestion

Question 18

What are lipids made up of?

Answer 18

1 glycerol + 3 fatty acids

Question 19

What are proteins made up of?

Answer 19

Amino acids

Question 20

Name the reagent used to test starch

Answer 20

Iodine

Question 21

What element make up proteins

Answer 21

Carbon, hydrogen, oxygen, nitrogen

Question 22

Name the reagent used to test proteins

Answer 22

Biuret solution

Question 23

Name the reagent used to test for sugars

Answer 23

Benedict’s solution

Question 24

Name the reagent used to test for lipids

Answer 24

Ethanol(+water)

Question 25

State risks of doing food tests

Answer 25

• Ethanol is flammable
• Biuret is corrosive

Question 26

Function of salivary glands

Answer 26

Produce digestive enzymes e.g. amylase

Question 27

Function of the stomach

Answer 27

Releases digestive enzymes to digest foods

Question 28

Digesting carbohydrates

Answer 28

• Starch is one of the most common carbohydrates we eat. It is brown down into sugars in the mouth and small intestine. This reaction is catalysed by an enzyme called amylase
• Amylase is produced in the salivary glands, so the digestion of starch starts in the mouth
• Amylase is also made in the pancreas, no digestion takes place inside the pancreas
• All the enzymes made there flow into the small intestine, where most starch is digested

Question 29

Digesting proteins

Answer 29

• The breakdown of protein food such as meat, fish, and cheese into amino acids is catalysed by protease enzymes
• Proteases are produced by the stomach, pancreas, and small intestine
• The breakdown of proteins into amino acids takes place in the stomach and small intestine

Question 30

Digesting fats

Answer 30

• Lipids are broken down into fatty acids and glycerol in the small intestine
• The reaction is catalysed by lipase enzymes, which are made in the pancreas and the small intestine, the enzymes made in the pancreas pass into the small intestine
• Bile emulsifies the fats, breaks up large drops of fat into smaller droplets, provides a much bigger surface area of fats for the lipase enzymes to act upon
• The larger surface area helps the lipase chemically break down the fats more quickly into fatty acids and glycerol

Question 31

What happens after digestion?

Answer 31

• Once the food molecules have been completely digested into soluble glucose, amino acids, fatty acids, and glycerol, they leave the small intestine
• They pass into the bloodstream to be carried around the body to the cells that need them

Question 32

Which organs produce amylase?

Answer 32

Salivary glands and pancreas

Question 33

Which organs produce proteases?

Answer 33

Stomach, pancreas, small intestine

Question 34

Which organs produce lipases?

Answer 34

Pancreas and small intestine

Question 35

Where does starch digestion occur?

Answer 35

Mouth and small intestine

Question 36

Where does protein digestion occur?

Answer 36

Stomach and small intestine

Question 37

Where does lipid digestion occur?

Answer 37

Small intestine

Question 38

Why do enzymes not work well at lower temperatures?

Answer 38

Inactive, not enough kinetic energy to collide and bind to the active site

Question 39

What is digestion?

Answer 39

Breakdown of large insoluble molecules into smaller soluble substances

Question 40

What is emulsification?

Answer 40

Physically breaking down large oil drops into smaller droplets, increasing surface area for lipases to work on

Question 41

What is the role of bile in the digestive system?

Answer 41

• Bile is an alkaline substance which neutralises the hydrochloric acid secreted by the stomach
• Bile emulsifies lipids to form droplets, this increases the surface area for the lipase enzyme to work on

Question 42

what is the main function of the digestive system?

Answer 42

to digest food and absorb nutrients obtained from digestion

Question 43

what is the role of the pancreas and salivary gland in the digestive system?

Answer 43

glands which produce digestive juices containing enzymes

Question 44

what is the role of the stomach in the digestive system?

Answer 44

• produces hydrochloric acid
• which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function

Question 45

what is the role of the small intestine in the digestive system?

Answer 45

where soluble food molecules are absorbed into the bloodstream

Question 46

what is the role of the liver in the digestive system?

Answer 46

• produces bile
• which emulsifies lipids and allow the lipase enzyme to work more efficiently

Question 47

what is the role of the large intestine in the digestive system?

Answer 47

absorbs water from undigested food, producing faeces

Question 48

what is the role of enzymes in the digestive system?

Answer 48

act as biological catalysts which speed up the rate of biological reactions (the breakdown of food) without being used up

Question 49

how does temperature affect enzyme action?

Answer 49

• up to a certain point, increasing temperature increases enzyme action
• as molecules have higher kinetic energy
• above optimum temperature, the shape of the active site is altered and the enzyme becomes denatured
• the substrate can no longer bind to the active site, so the reaction can no longer be catalysed

Question 50

where are proteases produced in the body?

Answer 50

stomach, pancreas and small intestine

Question 51

where are lipases produced in the body?

Answer 51

pancreas and small intestine

Question 52

which organs in the human digestive system produce amylase?

Answer 52

salivary gland, pancreas and small intestine